1. Field of the Invention
This invention relates to magnetic field sensors, a memory and a magnetic imager, and more particularly, to semiconductor Hall devices for simultaneously measuring magnetic fields with high spatial resolution in two directions.
2. Description of the Background Art
A Hall device is normally a four terminal device used for detecting a magnetic field. A semiconductor layer has two electrodes for passing electrical current in a first direction through the layer and two additional electrodes for detecting the voltage transverse to the electrical current at times when a magnetic field to be detected is passing through the semiconductor layer. The voltage on the terminals is known as the Hall voltage and is a measure of the magnetic field component orthogonal to the current passing through the layer.
One example of a Hall element is found in U.S. Pat. No. 5,055,820 which issued on Oct. 8, 1991 wherein several layers or substrates were combined to form a plurality of discrete Hall devices for measuring the magnetic field in several directions at the same time. The Hall devices were spatially distributed, therefore measuring the magnetic field or a component of the magnetic field in one direction at the location of the respective device. A linear array of Hall devices on a GaAs epitaxial film and imaging the critical state of a conventional superconductor Nb has been described in publications by T. Tamegai et al. in Phys. Rev. B, 45, 8201 (1992) and Phys. Rev. B, 4, 2589 (1992).